1. Field of the Invention
The present invention relates to an apparatus and a method for generating coefficient data of an estimating equation used for converting a first information signal to a second information signal, to an apparatus and a method for converting the first information signal to the second information signal using the coefficient data, to a program for causing a computer to execute these methods, and to a medium for recording the program.
In particular, the present invention relates to an apparatus for generating coefficient data of an estimating equation for obtaining information data of the second information signal at a position of interest, in which coefficient seed data, which are coefficient data of a generation equation for generating the coefficient data of the estimating equation, are determined by using a plurality of training data items acquired from a teacher signal corresponding to the second information signal and a student signal corresponding to the first information signal and similarity of a student part of the plurality of training data items with respect to a part of the first information signal corresponding to the position of interest in the second information signal. The generation equation includes the similarity as a parameter. Thus, the present invention relates to an apparatus for generating coefficient data to obtain information data at the position of interest in the second information signal and for always providing the optimal coefficient data of the estimating equation, and therefore, providing improved quality of the output according to the second information signal.
2. Description of the Related Art
In recent years, a large number of technologies for improving the resolution or sampling frequency of image signals and audio signals have been proposed. For example, in order to upconvert a standard television signal having a standard resolution or low resolution to a high-resolution signal, known as an HDTV signal, or in order to carry out a sub-sampling interpolation operation on the standard television signal, it is known that an adaptive classification method provides a better result in performance compared to a known interpolation method.
In the adaptive classification method, in order to convert a standard television signal (SD signal) having a standard resolution or low resolution to a high-resolution signal (HD signal), a class to which pixel data at a pixel position of interest in the HD signal belongs is detected. Then, the pixel data at the pixel position in the HD signal is generated from a plurality of pixel data items in the SD signal using an estimating equation and coefficient data of the equation corresponding to the class. The coefficient data of the equation used in the conversion process including the classification is determined by learning for each class, for example, using a least-square method.
For example, as is disclosed in Japanese Unexamined Patent Application Publication No. 2002-218414, coefficient seed data, which is coefficient data of a generation equation including a parameter for adjusting resolution, is predetermined by learning for each class, for example, using a least-square method. Using the coefficient seed data and the parameter value, coefficient data of an estimating equation used for the conversion process including classification is obtained based on the generation equation.
As described above, coefficient data of an estimating equation for obtaining pixel data at a pixel position of interest in an HD signal corresponds to a class to which the pixel data at the pixel position of interest in the HD signal belongs. The coefficient data can provide average pixel data that belongs to the class in high accuracy, but is not very appropriate for an estimating equation to obtain pixel data at a pixel position of interest in an HD signal.